vaillent ecotech 837 using lots of gas and doesnt heat house

[jkcov]

the meter is metric and the rating we got for the hw was 0.128 over 2 mins.
i meant by the modulating time it burns gas for the first 40 mins then uses the water vapour to keep the heating on for another 20mins before using gas again. i changed this to 30mins rather than the pre set 20 mins so 50% of the time it uses gas the other 50% uses vapour. This did not make a noticable difference.

 

[D_Hailsham]

the meter is metric and the rating we got for the hw was 0.128 over 2 mins.

That's equivalent to a consumption of 41kW. If your boiler is giving off 37kW, its efficiency is approx 90%.

i meant by the modulating time it burns gas for the first 40 mins then uses the water vapour to keep the heating on for another 20mins before using gas again. i changed this to 30mins rather than the pre set 20 mins so 50% of the time it uses gas the other 50% uses vapour.

Do you mean parameter d.2 (max anti cycling time)?

 

[jkcov]

Yeah sorry d.2. So based on the result and the boiler being 90% effiecent then its running correctly now. So maybe with the lack of heating ie not getting over 21c my new rads are undersized. Do you think that in the long rung im better keeping the 837 at 13kw for heating and put up with the 37kw hot water or replace the boiler with a lower spec model ie 824 and save on gas? thanks for ur advice

 

[jkcov]

What would you recommend i put the ch temp at the boiler on i think at the mo its 62c. If thats higher maybe the rads would get hotter and raise the temp above 20c

 

[David937]

What would you recommend i put the ch temp at the boiler on i think at the mo its 62c. If thats higher maybe the rads would get hotter and raise the temp above 20c

Try 70ºc, if that doesn't work try 75ºc, the aim is to keep it as low as possible to heat your house to the desired temperature.

 

[D_Hailsham]

Yeah sorry d.2.

Have a read of this

So maybe with the lack of heating ie not getting over 21c my new rads are undersized.

That's the first time you have said anything about the rads being new!
Were they replaced like for like? They should really have been replaced with ones which are about 20-25% larger to take into account the lower output when running with a 20°C differential.

Have you used the boiler sizer I gave a link to? What were the results?

What are your flow (d.40) and return (d.41) temperatures?

Just seen your next post. 62°C is too low a flow temp and would explain why you cannot get the house very hot. Try turning it up to 70°C or even 75°C.

Your old Flamingo had a maximum flow temp of 82°C and a return of 71°C. This means that the rads were giving off nearly 20% more than the manufacturer's spec says.

What controls do you have (programmer and thermostat)?

Do you think that in the long rung im better keeping the 837 at 13kw for heating and put up with the 37kw hot water or replace the boiler with a lower spec model ie 824 and save on gas?

I doubt if you would recover the cost of changing the boiler in savings on the gas bill - if there are any.

Did the installer measure the cold water flow rate before recommending the 837? If he didn't, you could argue that the boiler is not "fit for purpose" and insist that he replace it at his own cost. Trading Standards would be able to advise you on this.

You can measure the flow rate at the cold tap in the kitchen using a marked bucket and a watch. You need 2.5kW per litre/min to give a HW temperature of 40°C when the incoming water is at 5°C.